Employee Retirement Plans (Net Periodic Benefit Cost of Postretirement Benefits) (Details) - Postretirement Benefits [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 9	$ 10	$ 10
Interest cost	27	24	26
Amortization of net gain	(7)		(1)
Amortization of prior service credit		(7)	(3)
Recognition of actuarial gain	(1)
Total pension and postretirement benefit expense	28	27	32
Special termination benefit charge	1
Total expense	29	27	32
Current year actuarial loss (gain)	6	(47)	17
Amortization of actuarial net gain	1		1
Current year prior service cost/credit	5	(40)
Amortization of prior service (cost) credit	7	7	3
Total recognized in other comprehensive loss (income)	$ 19	$ (80)	$ 21